Osmotically active compounds (osmotics, osmotic agents) are widely used in the pharmaceutical and medical fields. For example, osmotics are used to adjust the tonicity of pharmaceutical drugs, in particular parenteral medications, where the osmotic pressure of a drug is adjusted to be hypotonic, hypertonic or isotonic, depending on how they are administered. For example, the osmotic pressure of a parenteral drug solution can be adjusted to the osmotic pressure of human blood by adding an osmotic agent (iso-osmotic solutions).
Furthermore, osmotics are used in dialysis treatments, in particular in peritoneal dialysis, to withdraw excess water from the dialysis patient.
The peritoneal dialysis process is based on the fact that a solution containing osmotically active compounds is introduced through a catheter into the peritoneal cavity of the dialysis patient. This solution left in the patient's abdominal cavity for a certain period of time (usually a few hours) and develops its osmotic effect there, i.e., endogenous water is withdrawn from the patient's abdominal cavity. After a certain dwell time, the peritoneal dialysis solution which is now dilute is drained out through a catheter.
This principle is used in various peritoneal dialysis treatment methods. For example, the methods of intermittent (IPD), nocturnal intermittent (NIPD), continuous cyclic (CCPD) or continuous ambulant peritoneal dialysis (CAPD) may be used as needed. Instruments used in IPD, NIPD and CCPD support the patient in performing the peritoneal dialysis method. CAPD is a manual method.
The addition of osmotically active compounds in particular should ensure that the osmotic pressure of the peritoneal dialysis solution is high enough during the entire dwell time in the abdominal cavity to withdraw water from the patient, i.e., water is transferred from the patient's circulation into his abdominal cavity (ultrafiltration).
However, because of the transfer of water into the abdominal cavity, the peritoneal dialysis solution introduced there is necessarily diluted. This dilution results in a decline in the concentration of the osmotically active compound and thus also the osmotic pressure of this solution.
If the osmotic pressure of the peritoneal dialysis solution declines because of this dilution, this in turn results in a decline in the transfer of water into the abdominal cavity per occurring per unit of time or it may stop entirely. In these cases, effective removal of water is no longer occurring with a progressively longer dwell time of the peritoneal dialysis solution in the patient's abdominal cavity.
The direction of transfer of water may even be reversed by absorption of osmotically active compounds into the patient's bloodstream, i.e., water is transferred out of the patient's abdominal cavity and into his bloodstream (negative ultrafiltration). This is the case when the dilute peritoneal dialysis solution in the abdominal cavity has a lower osmotic pressure than the endogenous water (e.g., the blood) of the patient.
By adding suitable osmotically active compounds to the peritoneal dialysis solution, the osmotic pressure can be maintained for a treatment time that is suitable for peritoneal dialysis, so there is not an excessive decline in ultrafiltration within the dwell time of the solution in the abdominal cavity. Negative ultrafiltration is thus also largely prevented.
The solutions used in the peritoneal dialysis treatment usually contain sugar monomers or polymers, such as glucose or polyglucose (e.g., starch derivatives), as osmotically active compounds.
EP-B1-0602585 proposes the use of hydroxyethyl starch as an osmotic.
EP-B1-0083360, EP-B2-0115911, EP-B1-0153164 and EP-B1-0207676 relate to solutions for peritoneal dialysis, containing starch hydrolysate-glucose polymers as osmotically active compounds.